• Remove ibus

sudo apt purge ibus
sudo apt autoremove

• Install Sogou Pinyin and dependencies

# Download deb installer from https://shurufa.sogou.com/linux
sudo dpkg -i <sogou_xxx.deb>
sudo apt install -f

# Additional dependencies (refer to: https://shurufa.sogou.com/linux/guide)
sudo apt install libqt5qml5 libqt5quick5 libqt5quickwidgets5 qml-module-qtquick2 libgsettings-qt1 

• Reboot
• At the login screen, when you type in the password, an icon shows up at the bottom-right of the screen. Click that icon to select 'Ubuntu on Xorg'. Then login.
• Right click the keyboard icon at the top-right of the screen, then click 'Configure', click '+', uncheck 'Only show current language', find 'sogoupinyin', click 'OK'.
• Done. Now you may switch to Sogou Pinyin via 'Ctrl-Space' hotkey.